The present invention relates to a method and to an arrangement for producing basic starting material for the production of fastener tabs that are intended to fasten together the side portions of absorbent articles, such as diapers or like-articles that include a front part, a back part and an intermediate crotch part, so that the article will have a pants-like configuration. The invention also relates to such basic starting material and to a fastener tab produced from such material.
Absorbent article fastener tabs used to fasten together the side portions of articles so that the article will have a pants-like configuration when worn are known in many different varieties. For instance, the tabs may be of a mechanical type that includes hooks of the touch-and-close fastener type or some like type, as described in EP-A1-0 235 014, for instance. Fastener tabs of this type, however, are expensive and difficult to apply at fast speeds in the manufacture of absorbent articles. Such tabs have therefore had limited use. WO-A1-95/05140 describes a fastener tab manufacturing method which is said to avoid these problems.
Other types of fastener devices that are more suited for application at high speeds are known to the art. For instance, it is known to provide a diaper with pressure-sensitive tape for fastening the diaper around the waist of a wearer, therewith fastening the front and back side of the diaper together to obtain a pants-like configuration. These tapes are often made of paper material and are therefore usually relatively rigid. These tapes are also often provided with some form of protective film that must be removed prior to use.
Elastic fastener devices are also known in the present context. For instance, U.S. Pat. No. 3,800,796 describes a disposable diaper that includes semi-elastic fastener tabs. The fastener tabs may comprise elastic material that forms an elastic zone surrounded by non-elastic material that forms two non-elastic zones, or may alternatively comprise solely elastic material that has been made non-elastic at its edge regions in some suitable manner. One of these non-elastic zones of the fastener tabs is fastened to the diaper and the other is provided with an adhesive substance, for instance.
One problem resides in the ability of producing both left-hand and right-hand fastener tabs simultaneously, which is desirable since pairs of left-hand and right-hand fastener tabs are often fastened simultaneously to mutually sequential absorbent article blanks in the continuous manufacture of such articles. Furthermore, it shall be possible to produce absorbent articles provided with such fastener tabs at high production rates. Difficulties may be experienced in applying glue and other adhesive substances.
The fastener tabs must also be soft, partially air permeable and must not chafe the skin of the wearer.
Furthermore, it is desirable that elastic fastener devices will include a xe2x80x9cstop functionxe2x80x9d that has a distinct stop which xe2x80x9cinformsxe2x80x9d the user or the carer when the elastic part has been stretched to a maximum, i.e. includes casing material that prevents further stretching of the elastic sheets or layers. This can be achieved with stretched elastic fastened to a non-elastic casing material. Alternatively, the casing material can be pleated and fastened to a smooth elastic material, which may be either in a stretched or a relaxed state.
Against this background of the aforesaid problems, a preferred method has been a laminating method in which the elastic is stretched and the casing materials are smooth, and in which the casing materials are joined together, suitably by heat welding or ultrasound welding.
EP-A1-0 494 941 describes a method of producing an elastic material, by joining two sheets of non-stretchable material that enclose a stretched elastic sheet, through the medium of perforations in the elastic sheet. This document also discloses that zones of different elastic properties can be produced through the medium of different perforation patterns and that non-elastic zones can also be produced, wherein the non-elastic zones are parts that were originally elastic but that have been xe2x80x9ckilledxe2x80x9d by intensive heat treatment or ultrasound welding. The resultant non-elastic zones are relatively dense, although they are air-permeable to some extent. Furthermore, the intensive treatment has a negative effect on the casing materials, which tend to become hard. The desired smooth surface is lost and the hard edges that are formed are very liable to chafe the wearer""s skin when coming into contact therewith. Further examples of similar elastic material are found in WO-A1-92/15444, for instance.
It is difficult to pleat casing materials prior to being fastened to the elastic material, because of the high precision required. This difficulty is more pronounced at high manufacturing rates. The application of glue becomes difficult. When the materials are not thermally miscible, problems also occur in heat sealing processes.
There are thus problems which known technology has been unable to solve.
The above problems are essentially avoided completely by the present invention. The object of the invention is to provide a method and arrangement for producing basic starting material for the production of fastener tabs that have different degrees of stretchability in different directions and that are intended for fastening absorbent articles around the wearer""s waist, and that can be produced in pairs at high production rates, and with which the use of adhesive agents can be limited. The fastener tabs shall also fulfil the requirement of softness, shall be air permeable and not cause chafing of the skin.
These objects are achieved in accordance with the invention with a method of producing basic starting material for the production of fastener tabs which are intended to join together the side-parts of the front and back portions of absorbent articles that include a front part, a back part and an intermediate crotch part so as to impart a pants-like configuration to said article, said method being characterised by the steps of
stretching a first sheet of elastic material in a first direction;
applying a second and a third sheet of material on respective opposite sides of the first sheet;
fastening the three sheets of material together in at least two mutually separate zones that extend parallel to each other in a second direction perpendicular to said first direction;
dividing the first sheet in each region between two zones along a line that lies between said zones, wherewith the first sheet in each region between two zones contracts to a non-stretched or relaxed state, and thereafter
fastening the three sheets of material together in each region between two zones.
In one preferred embodiment of the invention, the sheets of material are fastened together in each region between two zones in which the second and third sheets are fastened to the first sheet with said sheet in a stretched state and with the first sheet stretched in said zones.
In one alternative, the first sheet of material may be caused to contract to an unstretched state prior to the sheets being fastened together in each region between two zones, in which the second and third sheets are fastened to the first sheet with said sheet in a stretched state.
In one preferred embodiment of the invention, the first, second and third sheets of material are fastened together in two edge regions that extend in said second direction and that extend in said first direction outwardly of the nearest zone, in which the second and third sheets are fastened to the first sheet with said sheet in a stretched state subsequent to having caused said first sheet to contract to an unstretched state in the zones in which the second and third sheets have been fastened to the first sheet with said sheet in a stretched state.
Division of the first sheet in each region between two zones in which the second and third sheets are fastened to the first sheet with said sheet in a stretched state is effected by providing a line of perforations in the first sheet, wherein the spacing between said perforations is so small that the contracting force in the stretched first sheet is sufficient to pull the first sheet apart in the region between two mutually sequential perforations.
The invention also relates to an arrangement for the continuous production of basic starting material for the manufacture of fastener tabs that are intended to join the side-parts of the front and rear portions of absorbent articles that include a front part, a rear part and an intermediate crotch part, so as to impart a pants-like configuration to said article, said arrangement being characterised by means for advancing a first web of elastic material through said arrangement in one feed direction; means for stretching the first web transversely to the feed direction; means for applying a second and a third web of material onto respective opposite sides of said first web; means for fastening the combined webs together in at least two mutually separated zones that extend parallel with one another in said feed direction; means for dividing the first web in each region between two zones in which the three webs are fastened together with the first web in a stretched state, along a line that lies between said zones, wherein the first sheet of material in each region between two zones contracts to an unstretched or relaxed state; and means for fastening the webs together subsequent to the division of the first web in each region between two zones in which the three webs are fastened together with the first web in a stretched state.
According to one preferred embodiment, the arrangement includes means for bringing the stretched first web to an unstretched state, and downstream means in the feed direction for fastening the three webs together in the edge regions that extend in the feed direction outwardly of the transversely outermost zones in which the three webs of material are fastened together with the first web in a stretched state.
The means for bringing the stretched first web of material to an unstretched or relaxed state are preferably located downstream of the means for fastening the webs together in each region between two zones in which the three webs are fastened together with the first web in a stretched state, subsequent to having divided said first web. Alternatively, said means may be located immediately downstream of said means for dividing the first web of material in each region between two zones in which the three webs are fastened together with the first web in a stretched state.
The means for fastening said webs together will preferably have the form of an ultrasound welding unit or a heat welding unit. It is also possible to use different types of means for the different fastening operations. The means used to fasten the three webs together, with the first web in a stretched state, may alternatively have the form, of a gluing unit.
The means for dividing the first web in each region between two zones in which the three webs are fastened together with the first web in a stretched state, along a line that lies between said zones, may comprise a perforating device that perforates the first web. In the preferred embodiment, the perforating device is an ultrasound unit adapted to perforate the first web of material and to fasten the second and third webs together through the holes or openings created in the first web in said perforating process.
The invention also relates to a basic starting material for the production of fastener tabs which together function to fasten together the side-parts of an absorbent article that includes a front part, a rear part and an intermediate crotch part, so as to impart to the article a pants-like configuration, wherein the basic starting material has a length and a width, characterised in that said basic starting material includes at least two elastic zones that extend in the longitudinal direction of said material and that are mutually separated transversely by an intermediate non-elastic zone.
In one preferred embodiment, the elastic material extends from the elastic zones slightly into each non-elastic zone and the ratio between the transverse extension of the elastic zones in a maximum stretched state and in a relaxed state is smaller than or equal to the ratio of the transverse extension of the intermediate non-elastic zone to the sum of the transverse extension of those pieces of elastic material that extend into said zone.
The elastic zones include a layer or sheet of elastic material which is mounted in a stretched state between two sheets of material and fastened thereto, either directly or indirectly, said two sheets extending over each elastic and non-elastic zone. By xe2x80x9cfastened directlyxe2x80x9d is meant that the sheets, or layers, are directly fastened to each other as by gluing or ultrasound welding for instance, whereas by xe2x80x9cfastened indirectlyxe2x80x9d is meant that the two sheets or layers are fastened together via perforations in the intermediate sheet, in the manner described in the aforesaid EP-A1-0 404 941. At least one of the two sheets of material between which an elastic sheet is mounted in the elastic zones is comprised of a generally non-stretchable material, preferably a nonwoven material that will conveniently include thermoplastic fibres. In one advantageous variant, the two sheets of material between which an elastic sheet is mounted in the elastic zones are comprised of nonwoven material and both have mutually the same weight per unit area. In one preferred embodiment, both of said sheets are comprised of nonwoven material and have mutually different weights per unit area, wherewith one has a weight per unit area of 5-50 g/m2 while the other has a weight per unit area of between 10-80 g/m2. In one particularly preferred variant, at least one of the nonwoven sheets or layers is a spunbond nonwoven. Each elastic zone includes a sheet of elastic film, elastic foam, elastic net or a laminate that includes at least one elastic component.
The invention also relates to a fastener tab which is intended to be fastened to one side part of an absorbent article that includes a front part, a rear part and an intermediate crotch part, so as to join mutually coacting side-parts of the front and rear part of the article and therewith give the article a pants-like configuration, wherein the fastener tab has a user end and a manufacturer end and is characterised in that it includes a layer of elastic material which is fastened in a stretched state to two layers or sheets of generally unstretchable material, either directly or indirectly; in that the two unstretchable layers extend beyond the elastic layer so as to form an unstretchable end part; in that the elastic layer extends in a relaxed state slightly into the unstretchable end-part; and in that fastener means are mounted in the unstretchable end-part in the user end of one of the two unstretchable layers.
In one preferred embodiment, the unstretchable layers or sheets are comprised of nonwoven material of mutually different weights per unit area, and the fastener means are attached to the outside of the nonwoven sheet that has the lowest weight per unit area.
Finally, the invention relates to an absorbent article, such as a diaper or an incontinence protector, which is characterised by including a fastener tab according to the above.
Basic starting material produced in accordance with the method and by means of the inventive arrangement thus enables left-hand and right-hand fastener tabs to be produced at a high production rate while obtaining a soft and comfortable product.
An important feature of the fastener tabs and the basic starting material is that the elastic zone presents a clear stop in a maximum extended or stretched position. Furthermore, the non-elastic zone outwardly of the elastic zone on the fastener tabs and between the elastic zones of the basic starting material respectively shall be smooth so as to facilitate application of fastener elements, such as male fastener elements or female fastener elements in said zone. The basic starting material produced is continuous. A continuous web of material is mainly beneficial from a process/technical aspect, although not necessarily so.
Further preferred embodiments will be apparent from the detailed description of preferred embodiments given below with reference to the accompanying drawings.